IanS

Thanks for the advice. I bought NGK BPR6EY(V-power) plugs at Autozone yesterday, but everyone here is recommending BPR7ES's. Based on my spark plug pics, should I go a heat range colder, and should I stay with the EY''s(V-power) or the ES's?

I'm have an order with Paragon shipping tomorrow, so I'll have them add an O2 sensor to it.

I'll do an oil change after the fuel injector cleaner too.

-Ian

IanS

So far, I've started running a can of BG44k, and I also replaced the DV, because it wasn't holding vacuum, so now I'm getting about 1.6bar of boost according to the stock gauge, and the car feels a lot more responsive.

I tested the TPS today, because I've heard they can go bad, and mine seemed a bit off. It reads towards the high end of the spec range(700 ohms at idle, 4.2k at full throttle). And it has a bit of nonlinearity, especially coming off idle. I took it off and cleaned it with some electronic parts cleaner, and it seems a bit more linear, but not perfect and the idle and full throttle resistances are the same.

Is it worth replacing? Does anyone have an extra they'd like to sell me for a reasonable price? It doesn't seem like its worth $107, but I do occasionally get a bit of idle wobble(it'll randomly drop by 50 rpm), so if this would help that and generally make the car run better, I'd would like to replace it.

Thanks, Ian

racerx7

15mph, 1566 RPM,
CO2 14.5%, = car is running efficient ( numbers above 12% are good)
O2 0.42% = car is not running lean

HC Max 118, Avg 31, Me 145 (failed) = maybe misfire lots of things can
cause HC, but since your car does not seem to be running lean or
rich, I will go with missfire just for the readings.

CO Max 0.75, Avg 0.1, Me 0.45% = normal ( if it was higher your car
would be running rich )

NO Max 799, Avg 237, Me 1058ppm(failed) = NOx is cause by heat.
Is your EGR working? Maybe carbon build up. If timing is adjustable
on your car you could try to retard it just a little bit to lower the Nox.

Just of giggles I would also change your oil. Yes, this does make a difference
if you oil is old. Your numbers are very close. It seems like you just need
to change plugs, oil and drive it real hard on the freeway and then
you should be good to go.

H2Opumpr

Hmmm.

My failures in the past were similar, as is most 951's I've seen on this board.

The factory Gillete cats give up early, especially if you run lean, they can melt inside. I bought a low mileage used factory cat, and passed instantly... my numbers were similar High NOx and HC's. Do yourself a favor and get on the internet and study the basics of oxidation/ reduction reactions of combustion. This will better help you understand that in a modern 3 cell cat, if one cell is bad, then the rest of the reaction does not complete itself.

Of course this is in addition to basic tune-up stuff that has been stated previously.

Other possibilities not mentioned:
AFM out of whack (wiper track on AFM needs to be moved, or temp sensor inside is bad)
DME sensor giving an incorrect signal to DME ( rich/lean)
check o2 sensor wiring... not just the sensor, they melt if too close to the downpipe
vacuum leaks? high mileage and underhood temps crack and cause leaks

Have a pretest run so if you fail, numbers dont get sent to the DMV and you get labelled as a gross polluter.
Good luck

Jake951

Yes, O2 sensor wiring can be a problem. Another thing to check: there is a connector for the O2 sensor harness that clips onto a plastic bracket on the top center of the firewall. I've had poor connections develop on two occasions inside that connector. Unplug the connector, clean up the prongs if they look dirty or oxidized, and remake the connection.

IanS

I was under the impression our cars don't have any sort of EGR system?

I'm going to checkout the AFM, and clean/adjust it if it needs it.

I have one remaining vacuum leak on the line under the throttle body, and that part is already on the way. After that, I'll pressure test it one more time and be satisfied that its leak free.

Any comments on the TPS resisttances above? Is it worth replacing?

Thanks for all your help, I think the car will be generally running really well after getting all of these items taken care of.

-Ian

racerx7

I am not familiar with the smog equipment on 944’s. For a long time German where able to get around from using egr and air pump. But as the keep making tighter emission controls now the also use egr and air pump. If your old car does not have egr it would explain why you failed Nox.
Egr is a very easy way to cool down the cylinder head temp, hence lower Nox. Some of the newer German cars would adjust the valve timing as a way to lower Nox. I think your car is to old to use that technology. I think Porsche must have just got away with it because the car must have run clean enough when the car was new. Can you adjust the ign timing on this car? If so, just retard it a little bit.

I don’t know how much your o2 sensor cost. If it is expensive I would test it first. I would back probe the sensor with a graphing meter.
(not a DVM, DVM will just give you a average, not useful for this test). Add propane (to so vacuum line in the intake works good), this will drive your car rich and your meter should read around .7 to .9 volts. Turn the propane off and the meter should start switching from around .3 volts to .8 back and forth around 5 to 8 times a second. It goes without saying you can only do this test after the 02 sensor is good and
hot.

This should be a simple diagnostic to competent smog repair shop.


Someone else also said it is common for the cats to go bad on these car. I did not mention that because there are so expensive. A lot times people will replace them and solve the syptom but not the root cause. A cheap test that only tells you that is bad ( it does not tell if it is good ) is just hit
with your had or rubber mallet if you stuff rattling around = bad. If take your cat off and look in there and see stuff falling down = bad. A better test if you a newer car (obdii) is if you had a o2 sensor before and after the car, then you can just
see if the cat is doing its job.

IanS

I finished cleaning the TPS and it appears to be completely linear now. I also checked the AFM, and it measured smoothly already.

I pulled the fuel rail and injectors to take a look and they look pretty terrible. Here they are from #1 to #4. 3 have cracked caps and the third has the taller replacement cap I've heard about. I need to test them to see what their spray pattern is like and whethey they drip/leak. Do you think it is worth having them rebuilt at RC engineering or Marren, or would I do well to just get a new seal kit from Rennbay?

IanS

I'll check the DME today. I want to ensure the FQS is at 0 as well. Are there resistance specs for O2 sensors so I can check the wiring? I'm probably going to replace the O2 sensor as a preventative maintentance item anyway, since I already ordered it.

The last vacuum leak I've found is being taken care of tomorrow.

I ordered a set of rennbay injector seals and hopefully that'll help the spray pattern a bit too.

-Ian

IanS

The DME reading was good at 2k when the car was off. I may check it after the car has warmed up later, but that is probably not a problem.

Do we have a fuel quality setting? They mention it here: http://www.frwilk.com/944dme/ If we do have one, the plastic plug on my DME doesn't seem to have been messed with, so probably no one has adjusted it, which is good.

As peckster said, I should have taken care of what I thought was the reference sensor, but its actually the speed sensor, first. I took it out to clean it and in addition to being pretty dirty, it has two or three dents in the metal sensor and insulating is flaking off near the sensor itself. So I'm replacing it ASAP.

I also checked out the cat and it didn't make a terrible sound, but it does appear to be damaged. It is fairly dented on the largest section. I'm tempted to replace it with a generic, newer, smaller, higher-flowing model at a local muffler shop. I think that would be legal, even in California, on a car this old.

-Ian

PEvans

H20,

It looks like you are more up to speed on the CA emissions issue. My area just became subject to the more stringent CA test, which includes NOx, and my car barely made the NOx. My mechanic says this is sort of an ongoing challenge for 951s. My readings for HC and CO were OK, and as always I did the test just after a major service.

My 1986 951 has 220 k and probably the original cat. Is your solution to replace it with a lower-mileage factory cat?

IanS

I replaced the seals and tips on my injectors today with the Rennsport kit and it does seem to be idling and running a bit smoother. My tips were in terrible shape, as you can see. We'll see if that and the BG44k and new plugs and oil are enought to pass.

-Ian

IanS

I passed my test today. I am quite sure the key was running the 15mph test in 1st. I'm not sure I would have passed otherwise. As it was, I was close to failing CO and NO at 15mph in 1st.

Here are my numbers:
15mph: HC 64, CO 0.62, NO 789(max is 799!)
25mph: HC 27, CO 0.21, NO 389

The rpms were both around 2500, so I still think its weird that the 15mph test was so much higher. The only thing I can think of is the cat temp? I probably have an exhaust leak somewhere, which cause the cat not to heat up as quickly?

All the 25mph numbers were a fair amount lower than the previous test, so presumably the new plugs, injector seals, vac leaks, and other things I did helped some.

Thanks for your advice, Ian

pflyers

Hey Ian,

I live in South Pas. glad to see a 951 owner locally.
There's a smog place in burbank that I take my car. The owner is a young guy, late 20's early 30's who used to own a 951 and totally loves these cars. If you ask him I'm sure he'll make a deal with you to test your car without linking it up with Sacramento, it'll save you from getting tagged as a gross polluter.

There is also a porsche mechanic very close by who may be able to help you. Petes' Porsche in Burbank. Really nice guy and very reasonable. He knows the smog guy too and actually went up there for me and screwed around with my car while it was on the smog dyno to get it to pass.

The smog place is a test only place on Glenoaks just north of Western on the west side of the street.

IanS

Thanks for the hint, I'll keep that in mind for the next time around in 2 years. I don't think i was tagged as a gross polluter, since I wasn't 2x over the limit, but I think 944 Turbo's are perpetually Test Only cars in California, at least from what I've gathered here.

We should get together sometime. I'd like to compare my car to another 951, since I haven't ridden in many. My first goal is to get my car back to 'as-new' condition, but I don't know if I've achieved that yet or not.

-Ian